Biochemial and cell kinetics studies have implicated the endogenous amino acid, taurine, in the proliferation of L1210 leukemic cells in the mouse model. In the early stages of growth of intraperitoneally injected leukemic cells, taurine concentration was markedly increased. As the doubling time of the cells increased, so did levels of taurine. The change in taurine concentration can be shown to occur just prior to the change in rate of proliferation. The objective of this proposed research program is to determine the role that taurine plays in cell proliferation. In this proposal, biochemical (i.e., synthesis, uptake, and release), ultrastructural (i.e., autoradiographic localization), and cell kinetic (i.e., stages of growth) correlates will be examined in both normal and leukemic cells. The in vivo studies of L1210 mice will be expanded to include in vitro studies using normal and leukemic human blood cells. The effect of taurine on cell proliferation in both normal and leukemic cells and the effect of potential taurine antagonists (e.g., 2-amino-ethyl phosphonic acid) will be studied 1) to establish whether taurine antagonism will prevent cellular proliferation and 2) to determine if there is a differential effect of taurine in normal and leukemic cells. It is hope that our results will provide more sensitive biochemical methods for early detection, prevention, and treatment of leukemia.